The centre-back told his new club's official website: "I am very happy to sign for Chelsea, a world-famous club with a reputation for major success. I am delighted to be in the Premier League, the best league in the world, and can't wait to meet my team-mates and get going.

"I am still at the beginning of my career but I believe this is the place to develop and learn from some of the best players in the world."

Miazga, who was named the 2015 U.S. Soccer Young Male Player of the Year in December, had been with the Red Bulls since May 2013.

He told New York's official website: "I am forever grateful for my time at Red Bull for providing me with the opportunity to grow and develop into the player I am today.

"My experiences there have helped me fulfil my lifelong goal along with the support of my family, friends, and God.

"It was a dream come true to sign my first professional contract with my hometown club. I want to say thank you to the entire New York Red Bulls organisation including all of my coaches, teammates and staff that were there with me during my time with the club."

Miazga had less than a year to run on his current contract with the Red Bulls, and given his desire to test himself overseas, they were left with little choice but to sell now rather than lose him for nothing at the end of the 2016 MLS season.

Red Bulls sporting director Ali Curtis said: "It is a bittersweet day for the New York Red Bulls.

"We are very happy for Matt to get the opportunity but it is tough to see him leave after coming through our academy to the first team -- there is a different feel when one of your homegrown players leaves.

"We tried everything we could to keep Matt but we understand and respect his desire to play in Europe. Moving forward, we'll either reinforce the team from within our existing player pool or we will acquire a player from the international market. Additionally, the proceeds of this transfer provide us with greater resources to put back into our youth system."